Tri- and hexanuclear heterometallic Ni(II)-M(II) (M = Ca, Sr and Ba) bis(salamo)-type complexes: Synthesis, structure and fluorescence properties

Article abstract of DOI:10.1039/c7ra07826a

Three heterometallic Ni(ii)-M(ii) (M = Ca, Sr and Ba) complexes, two discrete heterotrinuclear complexes [Ni₂(L)Ca(OAc)₂(CH₃OH)₂]·2C₂H₅OH·2CHCl₃ (1) and [Ni₂(L)Sr(OAc)₂(CH₃OH)₂]·2CH₃OH·2CH₂Cl₂ (2) and a discrete heterohexanuclear dimer [Ni₂(L)Ba(OAc)₂(CH₃OH)₂(H₂O)]₂·2CH₃OH (3), were synthesized with a naphthalenediol-based acyclic bis(salamo)-type ligand (H₄L), and characterized by elemental analyses, IR, UV-vis spectra, fluorescence spectra and X-ray crystallography. The heterometallic complexes were acquired by the reaction of H₄L with 2 equiv. of Ni(OAc)₂·4H₂O and 1 equiv. of M(OAc)₂ (M = Ca, Sr and Ba). The crystal structures of complexes 1-3 have been determined by single-crystal X-ray diffractions. Owing to the different nature of the N₂O₂ and O₆ sites of the ligand H₄L, the introduction of two different metal(ii) atoms to the site-selective moiety, leads to the two Ni(ii) atoms occupied both the N₂O₂ sites, an alkaline earth metal atom occupied the O₆ site of the ligand (L)^4- unit, respectively. Furthermore, the fluorescence properties have been discussed.

Full text of DOI:10.1039/c7ra07826a

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Tri- and hexanuclear heterometallic Ni(II)–M(II) (M ¼
Ca, Sr and Ba) bis(salamo)-type complexes:
Cite this: RSC Adv., 2017, 7, 48394
synthesis, structure and fluorescence properties†
a
a
a
a
b
Xiu-Yan Dong, Xiao-Yan Li, Ling-Zhi Liu, Han Zhang, Yu-Jie Ding
a
and Wen-Kui Dong
*
Three heterometallic Ni(II)–M(II) (M ¼ Ca, Sr and Ba) complexes, two discrete heterotrinuclear complexes
Ni (L)Ca(OAc) (CH OH) ]$2C OH$2CHCl (1) and [Ni (L)Sr(OAc) (CH OH) ]$2CH OH$2CH Cl (2) and
a discrete heterohexanuclear dimer [Ni (L)Ba(OAc) (CH OH) (H O)] $2CH OH (3), were synthesized with
a naphthalenediol-based acyclic bis(salamo)-type ligand (H L), and characterized by elemental analyses,
IR, UV-vis spectra, fluorescence spectra and X-ray crystallography. The heterometallic complexes were
acquired by the reaction of H L with 2 equiv. of Ni(OAc) $4H O and 1 equiv. of M(OAc)
(M ¼ Ca, Sr and
Ba). The crystal structures of complexes 1–3 have been determined by single-crystal X-ray diffractions.
Owing to the different nature of the N and O sites of the ligand H L, the introduction of two
[
2
2
3
2
2
H
5
3
2
2
3
2
3
2
2
2
2
3
2
2
2
3
4
4
2
2
2
Received 16th July 2017
Accepted 10th October 2017
2
O
2
6
4
different metal(II) atoms to the site-selective moiety, leads to the two Ni(II) atoms occupied both the
DOI: 10.1039/c7ra07826a
4ꢀ
2
N O
2
sites, an alkaline earth metal atom occupied the O
6
site of the ligand (L)
unit, respectively.
rsc.li/rsc-advances
Furthermore, the fluorescence properties have been discussed.
10
sites and effectively control the guest recognition. Thus, the O
site of this type of ligands are particularly suitable for the larger
6
Introduction
The condensation between an aldehyde and an amine leading radius of the alkaline earth and rare earth metals to afford 3d–
to a salamo-type bisoxime was rst described by Nabeshima's 2s and 3d–4f heterometallic complexes exhibiting better crystal
1
2
group. Structurally, salen-type ligands are nitrogen analogue structures and photochemical properties.
of an aldehyde or ketone in which the carbonyl group (CO) has
Herein, as an extension of our previous studies, a new
been replaced by an imine or azomethine group. The properties acyclic bis(salamo)-type ligand H L is synthesized, in which two
salamo moieties share one naphthalenediol. As sizes of
and O cavities are different, it is possible to synthesize the
10
4
of salen-type ligands may be easily altered and as such they are
N
N
2
2
O
O
2
able to coordinate metals in a highly versatile way and combine
2
6
3
11,12
with O-donors to provide multidentate ligand systems. Salen- heterometallic complexes.
In this paper, heterometallic
type N
2
O
2
metal complexes are used as precursors to synthe- complexes [Ni
(L)Sr(OAc) (CH
OH) (H
2
(L)Ca(OAc)
OH) ]$2CH
O)] $2CH
2
(CH
3
OH)
2
]$2C
2
H
5
OH$2CHCl
(2) and [Ni
3
(1)
(L)
size the oligometallic complexes owing to the high coordination [Ni
ability of the phenoxo groups which can bridge two metal Ba(OAc)
OH$2CH
Cl
2
2
3
2
3
2
2
2
2
(CH
3
2
2
2
3
OH (3) have been synthesized
-acetate ions
-fashion, another
2
-acetate ion chelates Sr(II) atom as a bidentate ligand. In
4
centers in a m -M–O–M fashion. Then, such m -phenoxo and structurally characterized. In complex 2, two m
2
2
2
bridging is also particularly important for the d-block homo- bridge Ni(II) and Sr(II) atoms in a common m
2
and heterometallic complexes of salen-type ligands, some of
m
#
2
5
6
7
which exhibit interesting catalysis, sensors, electrochemical,
complex 3, two m
2
-acetate ions bridge the Ba1 and Ba1 atoms
8
9
luminescence and magnetism. In recent years, our group has in a familiar m -fashion, nally forming a hetero-hexanuclear
2
4ꢀ
2+
focused on the conversion of an acyclic molecule (bis(salamo)- dimer. To our knowledge, this novel 2 : 6 ((L) : M ) hetero-
type ligand) to the corresponding cyclic metal host, which can hexanuclear complex isn't reported in the bis(salamo)-type
1,2e,11c
afford a larger C-shaped O
6
site on the metalation of the N
2
O
2
complexes.
Experimental
Materials and general methods
a
School of Chemical and Biological Engineering, Lanzhou Jiaotong University,
Lanzhou, Gansu 730070, PR China. E-mail: dongwk@126.com
b
School of Biological & Chemical Engineering, Anhui Polytechnic University, Wuhu
2-Hydroxy-3-methoxybenzaldehyde (99%), methyl trioctyl
2
41000, PR China
ammonium chloride (90%), pyridiniumchlorochromate (98%)
and borontribromide (99.9%) were purchased from Alfa Aesar.
Hydrobromic acid 33 wt% solution in acetic acid was purchased
†
Electronic supplementary information (ESI) available. CCDC 1562392–1562394.
For ESI and crystallographic data in CIF or other electronic format see DOI:
0.1039/c7ra07826a
1
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from J&K Scientic Ltd. The other reagents and solvents were
purchased from Shanghai Darui Chemical Fine Chemicals
Company. Elemental analyses were performed by using
a GmbH Vario EL V3.00 automatic elemental analysis instru-
ment. Elemental analyses for metals were detected with an IRIS
ER/S-WP-1 ICP atomic emission spectrometer. FT-IR spectra
were recorded on a VERTEX70 FT-IR spectrophotometer, with
ꢀ
1
samples prepared as KBr (400–4000 cm ) pellets. UV-vis
absorption spectra were recorded on a Hitachi U-3900H spec-
1
13
trometer. H and C NMR spectra were determined by German
Bruker AVANCE DRX-400 spectrometer. Fluorescent spectra
were taken on a LS-55 uorescence photometer. X-ray single Scheme 2 Synthesis of heterometallic Ni(II)–M(II) complexes 1–3.
crystal structure determinations were carried out on a Super-
Nova, Dual, Cu at zero, Eos four-circle diffractometer. FTICR-MS
spectra were obtained on a Bruker Daltonics APEX-II 47e spec- (Fig. S2†). HRMS m/z: calc. for C H N O Na: [H L + Na]
+
3
2
32
4
10
4
trometer. Melting points were obtained with the use of an X4 655.20, found: 655.2011 (Fig. S3†). Elemental analysis: anal.
microscopic melting point apparatus made by the Beijing Taike calc. for C H N O : C, 60.75; H, 5.10; N, 8.86, found (%): C,
3
2
32 4 10
ꢀ
1
Instrument Limited Company and were uncorrected.
60.38; H, 5.38; N, 8.65. IR (KBr; cm ): 1604 [n(C]N)], 1248
[
(
n(Ar–O)], 3172 [n(O–H)]. UV-vis [in methanol/dichloromethane
1 : 1)], lmax (nm) [2.5 ꢂ 10 M]: 267, 341, 356, 376.
ꢀ5
Synthesis of the ligand H
The reaction steps involved in the synthesis of the bis(salamo)-
type tetraoxime ligand (H L) are shown in Scheme 1. 2,3-
Dihydroxynaphthalene-1,4-dicarbaldehyde was prepared Heterometallic complexes were synthesized by the reaction of
according to a literature procedure; 1,2-bis(aminooxy)ethane
4
L
Preparation of complexes 1–3
4
13
14
H
4
L with Ni(OAc) (M(II) ¼ Ca, Sr and Ba)
were (Scheme 2).
2 2
A solution of Ni(OAc) $4H O (9.96 mg, 0.040 mmol) in
2
$4H
2
O and M(OAc)
2
15
and 2-[O-(1-ethyloxyamide)]oxime-6-methoxyphenol
synthesized according to an analogous method.
A solution of 2,3-dihydroxynaphthalene-1,4-dicarbaldehyde ethanol (2 mL) and Ca(OAc) (3.16 mg, 0.020 mmol) in water/
2
(432.08 mg, 2 mmol) in ethanol (20 mL) was added dropwise methanol (1 : 3, 2 mL) were added to a solution of H4L
to a solution of 2-[O-(1-ethyloxyamide)]oxime-6-methoxyphenol (12.64 mg, 0.020 mmol) in chloroform (4 mL), and the resulting
904.4 mg, 4 mmol) in ethanol (20 mL) under room tempera- solution was evaporated to dryness, aer which the residue was
(
ture, the mixture was heated to reux and kept reuxing for 6 h. added to dichloromethane/methanol (1 : 1, 8 mL) and heated to
Then cooled down to room temperature and the yellow dissolve it and then cooled in the refrigerator and recrystallized.
precipitates were ltered and washed successively with ethanol The color of the mixed solution turned dark green. The mixture
and n-hexane, respectively. Several light yellow powdery solid was ltered and the ltrate was allowed to stand at room
(
H L) were obtained and collected by ltration, washed with temperature for approximately three weeks. The solvent was
4
absolute ethanol and dried under vacuum. Yield: 712.63 mg, partially evaporated and several clear dark green prismatic
ꢁ
6.36%; mp: 172 C; H NMR (CDCl , 400 MHz) d 11.03 (s, 2H, single crystals of complex 1 were obtained.
3
1
5
OH), 9.82 (s, 2H, OH), 9.14 (s, 2H, CH]N), 8.29 (s, 2H, CH]N),
A solution of Ni(OAc)
.97 (q, J ¼ 3.2 Hz, 2H, ArH), 7.41 (q, J ¼ 6.0, 2.9 Hz, 2H, ArH), methanol (2 mL) and Sr(OAc)
4
.06–6.68 (m, 6H, ArH), 4.58 (t, 8H, CH ), 3.89 (s, 6H, CH methanol (1 : 3, 2 mL) were added to a solution of H L
2
$4H
2
O (9.96 mg, 0.040 mmol) in
7
7
2
(3.16 mg, 0.020 mmol) in water/
2
3
)
1
3
(Fig. S1†). C NMR (DMSO, 151 MHz) d 148.4 (s), 148.2 (s), 147.3 (12.64 mg, 0.020 mmol) in dichloromethane (4 mL). The next
s), 147.2 (s), 146.1 (s), 126.2 (s), 125.4 (s), 123.9 (s), 119.7 (s), steps are similar to complex 1. Complex 3 was prepared by
(
119.0 (s), 118.4 (s), 113.7 (s), 111.4 (s), 73.0 (s), 72.8 (s), 56.3 (s) a similar procedure as for complex 2.
4
Scheme 1 Synthetic route to the bis(salamo)-type tetraoxime ligand H L.
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Table 1 Crystallographic data and refinement parameters for complexes 1, 2 and 3
Complex
Formula
1
C
2
C
3
C
44
H
56Cl
6
CaN
4
O18Ni
2
42
H
54Cl
4
SrN
4
O
18Ni
2
78 2 8 4
H96Ba N O36Ni
Formula weight
T (K)
Radiation (A)
1299.12
291(2)
Mo Ka, 0.71073
1247.99
155(10)
Mo Ka, 0.71073
Orthorhombic
Pbcn
23.6620(5)
17.8187(5)
12.4666(3)
90
90
90
5256.2(2)
4
1.579
2230.14
294(14)
Mo Ka, 0.71073
Monoclinic
1
P2 /n
15.8005(3)
15.7041(3)
18.2762(4)
90
94.551(19)
90
4520.62(16)
4
1.639
˚
Crystal system
Space group
Monoclinic
P2
1
/n
˚
a (A)
15.4086(8)
12.0628(6)
29.5294(9)
90
100.627(5)
90
5394.5(4)
4
1.600
˚
b (A)
˚
c (A)
ꢁ
a ( )
ꢁ
b ( )
ꢁ
g ( )
3
˚
Volume (A )
Z
D
ꢀ3
c
(g cm
)
ꢀ
ꢁ
1
Absorption coefficient (mm
Q range for data collection( )
F (000)
)
1.164
1.397 to 25.997
2680
1.996
3.862 to 24.112
2560.0
1.764
3.510 to 27.218
2264.0
Index ranges
ꢀ19 # h # 13,
ꢀ23 # h # 29,
ꢀ21 # k # 21
ꢀ15 # l # 15,
ꢀ18 # h # 18,
ꢀ14 # k # 18
ꢀ21 # l # 21,
ꢀ
ꢀ
14 # k # 13,
36 # l # 35,
Crystal size (mm)
0.24 ꢂ 0.22 ꢂ 0.20
0.21 ꢂ 0.22 ꢂ 0.24
0.15 ꢂ 0.17 ꢂ 0.21
17 095/7925 [Rint ¼ 0.030]
7925
Reections collected
Independent reection
Data/restraints/parameters
Final R indices [I > 2s(I)]
R indices (all data)
21 343/10 337 [Rint ¼ 0.0117]
16 016/5173 [Rint ¼ 0.050]
10 337
5173
10 337/12/642
5173/3/329
7925/45/600
a
R
R
1
¼ 0.0469, wR
¼ 0.0645, wR
P
2
¼ 0.0959
¼ 0.0986
R
R
1
¼ 0.0479, wR
2
¼ 0.0888
R
R
1
¼ 0.0365, wR
2
2
¼ 0.0760
¼ 0.0874
b
1
2
1
¼ 0.082, wR
2
¼ 0.1022
1
¼ 0.0546, wR
a
R
1
¼
P||F
o
| ꢀ |F
c
||/P
|F
o
|. wR
2
¼ [P
w(F
ꢀ F
c
) / w(F
o
) ] , w ¼ [s (F
) + (0.0784P) + 1.3233P]ꢀ1, where P ¼ (F 2
o
+ 2F
)/3.
b
2
o
2 2
2 2 1/2
2
2
o
2
2
c
2
Complex 1, dark green crystals, yields 12.57 mg, 48.37%. method on F . Anisotropic thermal parameters were used for
Elemental analysis: anal. calc. for C H Cl CaN O Ni (%): C the nonhydrogen atoms and isotropic parameters for the
4
4
56
6
4
18
2
4
4
1
0.68; H 4.34; N 4.31; Ni 9.04; Ca 3.09. Found (%): C 40.25; H hydrogen atoms. Hydrogen atoms were added geometrically
ꢀ
1
.31; N 4.62; Ni 8.98; Ca 3.01. IR (KBr; cm ): 1599 [n(C]N)], and rened using a riding model. The crystallographic data are
231 [n(Ar–O)], 3413 [n(O–H)]. UV-vis [in methanol/ summarized in Table 1. CCDC – 1562392 (1), 1562393 (2) and
ꢀ
5
dichloromethane (1 : 1)], lmax (nm) [2.5 ꢂ 10 M]: 284, 370.
1562394 (3)† contain the supplementary crystallographic data
Complex 2, dark green crystals, yields 11.14 mg, 44.65%. for this paper.
Elemental analysis: anal. calc. for C42
H54Cl
4
4 2
SrN O18Ni (%): C
4
4
1
0.37; H 4.36; N 4.48; Ni 9.39; Sr 7.01. Found (%): C 40.25; H
.31; N 4.62; Ni 9.26; Sr 6.92. IR (KBr; cm ): 1597 [n(C]N)],
Results and discussion
ꢀ1
233 [n(Ar–O)], 3413 [n(O–H)]. UV-vis [in methanol/ The ligand H L and its corresponding metal complexes 1–3 are
4
ꢀ
5
dichloromethane (1 : 1)], lmax (nm) [2.5 ꢂ 10 M]: 284, 370.
Complex 3, dark green crystals, yields 17.26 mg, 38.69%. DMSO, but slightly soluble in ethyl acetate, acetone, acetoni-
Elemental analysis: anal. calc. for C78 (%): C trile, methanol and ethanol. Complexes 1–3 are absolutely
1.99; H 4.34; N 5.02; Ni 10.52; Ba 12.31. Found (%): C 41.82; H soluble in DMF and DMSO, but slightly soluble in chloroform,
4
stable in air. The ligand H L is remarkably soluble in DMF and
2 8 4
H96Ba N O36Ni
4
4
1
ꢀ
1
.28; N 5.96; Ni 10.47; Ba 12.26. IR (KBr; cm ): 1593 [n(C]N)], dichloromethane, methanol and ethanol at room temperature.
1
242 [n(Ar–O)], 3402 [n(O–H)]. UV-vis [in methanol/
In the H NMR spectrum of H L, the peaks of methylene
4
ꢀ
5
dichloromethane (1 : 1)], lmax (nm) [2.5 ꢂ 10 M]: 284, 370.
protons were observed ca. at 4.58 ppm, and the peaks of oxime
protons were observed at 8.29 and 9.14 ppm. The OH reso-
nances at 9.82 and 11.03 ppm strongly, respectively, showing
X-ray crystallographic analysis
1
3
4
the symmetrical structure of H L (Fig. S1†). In the C NMR
The single crystals of complexes 1–3 were placed on a Super-
Nova, Dual, Cu at zero, Eos four-circle diffractometer. The
diffraction data were collected using a graphite mono-
spectrum of H L, the peaks of the C]N carbon atoms were
4
observed at 148.2 and 148.4 ppm, and the signals of CH carbon
atoms were observed at 56.31 ppm (Fig. S2†).
3
˚
chromated Mo Ka radiation (l ¼ 0.71073 A). Reection data
were corrected for Lorentz and polarization factor sand for
16
IR spectra analyses
absorption using the multi-scan method. The structures were
solved by using the program SHELXL-2016 and Fourier differ- IR spectra of H
ence techniques, and rened by the full-matrix least-squares 1–3 exhibit various bands in the region of 4000–400 cm
4
L and its corresponding Ni(II)–M(II) complexes
ꢀ
1
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Fig. 2 UV-vis spectra of the ligand H
L and its corresponding complexes 1–3 in methanol/dichloromethane (1 : 1) (c ¼ 2.5 ꢂ 10 M).
4
L and its corresponding complexes
ꢀ5
Fig. 1 IR spectra of the ligand H
4
1–3.
The uorescent properties of H L was determined in DMF
4
ꢀ5
ꢀ1
(
4
Fig. 1). The O–H stretching band of the free ligand H L has
solution (2.5 ꢂ 10 mol L ) by addition of Ni(OAc)
2
$4H
O (1 : 1) solu-
2
O,
ꢀ
1
been observed at ca. 3172 cm that belongs to the phenolic
hydroxyl group, whereas complex 1, 2 and 3 shows a band at ca.
3
Ca(OAc)
2
, Sr(OAc)
2
and Ba(OAc)
2
in methanol/H
2
ꢀ
3
ꢀ1
tion (1 ꢂ 10 mol L ) are shown in Fig. 3.
ꢀ
1
413, 3413 and 3402 cm that belongs to coordinated meth-
The excitation wavelengths of these complexes were measured
several times by using the maximum absorption wavelengths,
which is the UV-vis spectral theoretical excitation wavelength. The
optimal excitation wavelength of these complexes at 378 nm with
the maximum emission wavelength is 437 nm.
17
anol molecules.
4
The free ligand H L exhibits characteristic C]N stretching
ꢀ
1
ꢀ1
band at ca. 1604 cm , which is shied by ca. 5, 7, 11 cm in
complexes 1, 2 and 3, respectively, indicating that the nitrogen
atoms of C]N group are coordinated to the Ni(II) atoms,
18
The uorescence titration experiment were measured by the
19
2+
which is similar to previously reported Ni(II) complexes.
4
addition of Ni is shown in Fig. 3(a), the free ligand H L shows
ꢀ1
The Ar–O stretching frequency appears at ca. 1248 cm for the
ligand H L, while the Ar–O stretching frequencies in complexes 1,
and 3 are observed at ca. 1231, 1233 and 1242 cm , respectively.
remarkable uorescence quenching with maximum emission at
2
+
4
ca. 437 nm upon the addition of Ni . When the added amount
ꢀ
1
2
+
2
of the Ni reached 3.0 equiv., the uorescence emission
intensity almost complete quenching and became stable.
Weakened of uorescence is possible due to the coordination of
The Ar–O stretching frequencies are shied to lower frequencies,
indicating that the M–O bonds are formed between the metal(II)
atoms and oxygen atoms of phenolic groups.
20
24
metal ion with the ligand. The spectroscopic titration indi-
2
+
cated that the stoichiometric ratio between Ni and ligand unit
4
ꢀ
6c,18b
(
L) was 3 : 1, which signify the Ni(II) complex was formed.
UV-vis spectra analyses and uorescence properties
2+
2+
2+
Then, Ca , Sr and Ba were added to the Ni(II) complex,
The methanol/dichloromethane (1 : 1) solutions of the ligand respectively. As shown in Fig. 3(b)–(d), the uorescence inten-
2
+
H
4
L and its heterometallic Ni(II)–M(II) complexes show, as ex- sity gradually increased, when the added amount of the Ca
pected, almost identical UV-vis spectra (Fig. 2).
reached 1.0 equiv., the uorescence intensity reached the
The free ligand H
L shows four absorption peaks at 267, 341, maximum, which because one Ni in the Ni(II) complex was
56 and 376 nm. The absorption peak at 267 nm can be assigned replaced by one Ca , Sr or Ba , respectively.
to the p–p* transition of the benzene rings and the other bands at phenomenon may be due to the difference between the radius
2
+
4
2
+
2+
2+
6c,18b
3
This
2
+
3
41, 356 and 376 nm can be attributed to the intra-ligand n–p* of the Ni and the alkaline earth metal ion.
2
+
2+
2+
transition of the C]N bonds and conjugated aromatic chromo-
Titration of Ni(II) complex with Ca , Sr or Ba were fol-
L, lowed by uorescence spectroscopy to determine the binding
21
phore. Compared to the absorption peaks of the free ligand H
4
with the emergence of two absorption peaks at ca. 284 and 370 nm constant, respectively. As shown in Fig. S4,† the binding
2
+
2+
2+
are observed in complexes 1–3, which can be assigned to p–p* constant K of Ni(II) complex with Ca , Sr and Ba were esti-
3
ꢀ1
3
ꢀ1
2
ꢀ1
type transition (MLCT). The absorption peaks of complexes 1–3 mated to be 8.14 ꢂ 10 M , 3.01 ꢂ 10 M and 8.82 ꢂ 10 M
22
4ꢀ
are bathochromically shied, indicating coordination of (L)
by the Benesi–Hildebrand equation (uorescence method) way,
ligand unit. The coordination of metal atoms to the binding sites respectively, which unambiguously demonstrates stronger
of N O and hydroxyl oxygen of the naphthalene ring breaks the binding ability of Ni(II) complex with Ca .
25
2
+
2
2
intramolecular hydrogen-bonding interactions of H4L and
According to the obtained experimental data, the differences
increases the coplanarity of the conjugated system which causes among the three heterometallic complexes are very obvious and
23
changes in the UV-vis spectra.
could be utilized in host–guest systems.
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2+
4
Fig. 3 (a) Absorption spectra of H L in DMF solution upon the addition of Ni . (b) Absorption spectra of the Ni(II) complex in DMF solution upon
2
+
2+
the addition of Ca . (c) Absorption spectra of the Ni(II) complex in DMF solution upon the addition of Sr . (d) Absorption spectra of the Ni(II)
2+
complex in DMF solution upon the addition of Ba
.
Description of the crystal structures
(O14 or O11) from the m
2
-acetate bridge and one oxygen atom
(
O15 or O16) from the coordinated methanol molecule. Because
The crystal structures of the heterometallic complexes 1–3 were
determined by single-crystal X-ray diffraction. Selected bond
lengths and angles of complexes 1–3 are listed in Table 2.
of Ni1 and Ni2 are symmetry related, they have identical
geometries. Thus, the Ni1 and Ni2 atoms are both hexa-
coordinated with slightly distorted octahedral geometries.
While the central Ca1 atom is located in the O cavity, the four
are phenoxy oxygen atoms (O2, O5, O6 and O9) while two others
26
6
Crystal structure of complexes 1 and 2
(
O1 and O10) come from methoxy groups. Besides, two m2-
The crystal structures and atom numberings of complexes 1 and
acetate ions bridge the two terminal Ni(II) atoms and the central
Ca(II) atom in a m -fashion. So the Ca1 atom is octa-coordinated
2
are shown in Fig. 4 and 5, respectively. X-ray crystallographic
analysis of complex 1 reveals a trinuclear structure. It crystal-
2
with a slightly distorted square antiprism geometry. The Ca1
lizes in the monoclinic system, space group P2
of two Ni(II) atoms, one Ca(II) atom, one (L) unit, two m
acetate ions, two coordinated methanol molecules and two
crystallized ethanol and chloroform molecules. While complex
1
/n, and consists
4
ꢀ
atom of complex 1 has strong coordination with the four phe-
2
-
4
ꢀ
noxy oxygen atoms (O2, O5, O6 and O9) of the (L) units and
the two oxygen atoms (O12 and O13) of the m -acetate ions by
2
analyzing the distances of the eight Ca1–O bonds. The distances
between the Ca1 atom and the four phenoxy oxygen atoms (O2,
2
crystallizes in the orthorhombic crystal system, space group
4ꢀ
Pbcn, and consists of two Ni(II) atoms, one Sr(II) atom, one (L)
O5, O6 and O9) and the two m
O13) are ranged from 2.386(2) to 2.409(2) A, which are obviously
shorter than the distances of the other two Ca1–O bonds (Ca1–
2
-acetate oxygen atoms (O12 and
2
unit, two m -acetate ions, two coordinated methanol molecules
and two crystallized methanol and dichloromethane molecules.
X-ray crystallography clearly shows the formation of complexes
˚
˚
˚
O1 2.609(2) A and Ca1–O10 2.605(2) A). The coordination of
complex 2 is similar to that of complex 1. In the crystal structure of
complex 2, the distances between the Sr1 atom and the four
1
and 2, which was isolated as dark green crystals.
Interestingly, the formation process of complex 1 was highly
cooperative. In the crystal structure of complex 1, the terminal
Ni(II) atom (Ni1 or Ni2) is located in the N coordination
cavity of completely deprotonated (L) unit, one oxygen atom
#1
#1
phenoxy oxygen atoms (O2, O5, O2 and O5 ) and the two m -
acetate oxygen atoms (O7 and O7 ) are ranged from 2.511(2) to
2
O
2
2
#1
4
ꢀ
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ꢁ
a
Table 2 Selected bond lengths ( A˚ ) and angles ( ) of complexes 1, 2 and 3
Complex 1
Ni1–O2
Ni1–O15
Ni2–O6
Ni2–O16
Ca1–O1
Ca1–O6
Ca1–O12
2.020(2)
2.196(2)
1.968(2)
2.179(2)
2.609(2)
2.404(2)
2.393(2)
83.63(9)
86.59(10)
85.37(9)
176.37(9)
87.42(10)
83.04(8)
88.35(10)
88.79(9)
177.70(8)
84.83(10)
61.28(7)
102.73(7)
117.57(8)
161.47(8)
77.80(8)
151.85(8)
66.68(7)
90.21(8)
104.34(8)
164.39(8)
Ni1–O5
Ni1–N1
Ni2–O9
Ni2–N3
Ca1–O2
Ca1–O9
Ca1–O13
1.963(2)
2.071(3)
2.018(2)
2.066(3)
2.405(2)
2.404(2)
2.409(2)
91.39(9)
169.72(10)
167.96(11)
96.21(10)
84.38(10)
92.06(9)
168.08(11)
169.62(10)
93.92(10)
86.88(10)
120.48(8)
69.83(7)
67.31(7)
102.24(7)
64.54(7)
90.77(8)
119.98(8)
61.33(7)
117.38(8)
Ni1–O14
Ni1–N2
Ni2–O11
Ni2–N4
Ca1–O5
Ca1–O10
2.079(2)
2.062(2)
2.082(2)
2.055(3)
2.386(2)
2.605(2)
O2–Ni1–O5
O2–Ni1–N1
O5–Ni1–O15
O14–Ni1–O15
O15–Ni1–N1
O6–Ni2–O9
O6–Ni2–N3
O9–Ni2–O16
O11–Ni2–O16
O16–Ni2–N3
O1–Ca1–O2
O1–Ca1–O9
O1–Ca1–O13
O2–Ca1–O9
O2–Ca1–O13
O5–Ca1–O10
O6–Ca1–O9
O6–Ca1–O13
O9–Ca1–O13
O12–Ca1–O13
O2–Ni1–O14
O2–Ni1–N2
O5–Ni1–N1
O14–Ni1–N1
O15–Ni1–N2
O6–Ni2–O11
O6–Ni2–N4
O9–Ni2–N3
O11–Ni2–N3
O16–Ni2–N4
O1–Ca1–O5
O1–Ca1–O10
O2–Ca1–O5
O2–Ca1–O10
O5–Ca1–O6
O5–Ca1–O12
O6–Ca1–O10
O9–Ca1–O10
O10–Ca1–O12
O2–Ni1–O15
O5–Ni1–O14
O5–Ni1–N2
O14–Ni1–N2
N1–Ni1–N2
O6–Ni2–O16
O9–Ni2–O11
O9–Ni2–N4
O11–Ni2–N4
N3–Ni2–N4
O1–Ca1–O6
O1–Ca1–O12
O2–Ca1–O6
O2–Ca1–O12
O5–Ca1–O9
O5–Ca1–O13
O6–Ca1–O12
O9–Ca1–O12
O10–Ca1–O13
88.79(9)
91.05(9)
88.15(10)
94.94(11)
100.74(11)
85.99(9)
92.18(9)
87.27(10)
95.25(10)
100.51(11)
152.21(8)
76.33(8)
131.84(7)
105.29(8)
131.22(8)
76.17(8)
76.28(8)
77.73(8)
76.06(8)
Complex 2
Ni1–O2
Ni1–O8
Sr1–O1
2.011(3)
2.169(3)
2.667(3)
2.525(3)
2.511(2)
86.26(10)
86.72(12)
86.08(11)
178.00(10)
87.51(12)
60.20(8)
76.99(1)
76.83(9)
108.97(8)
105.89(8)
126.78(8)
76.83(9)
163.99(10)
116.49(9)
73.27(9)
Ni1–O5
Ni1–N1
Sr1–O2#
1.984(2)
2.068(3)
2.517(2)
2.667(3)
2.525(3)
91.73(10)
170.41(12)
170.72(12)
94.07(12)
85.68(12)
118.79(8)
108.97(8)
65.81(8)
167.40(8)
73.26(9)
61.16(8)
105.89(8)
60.21(8)
65.81(8)
Ni1–O6
Ni1–N2
Sr1–O5
2.063(3)
2.042(3)
2.511(2)
2.517(2)
1
#1
Sr1–O7#
Sr1–O1
Sr1–O2
1
#1
Sr1–O5
Sr1–O7
O2–Ni1–O5
O2–Ni1–N1
O5–Ni1–O8
O6–Ni1–O8
O8–Ni1–N1
O1–Sr1–O2#
O2–Ni1–O6
O2–Ni1–N2
O5–Ni1–N1
O6–Ni1–N1
O8–Ni1–N2
O1–Sr1–O5
O1–Sr1–O2
O2–Sr1–O5
O2–Sr1–O2
O5–Sr1–O7
O2–Ni1–O8
O5–Ni1–O6
O5–Ni1–N2
O6–Ni1–N2
N1–Ni1–N2
O1–Sr1–O7
O1–Sr1–O5
O2–Sr1–O7
O2–Sr1–O5
O5–Sr1–O1
87.13(10)
92.21(10)
86.94(12)
95.27(12)
99.27(14)
116.48(9)
150.00(8)
75.92(8)
126.78(8)
150.00(8)
92.77(9)
92.76(9)
118.79(8)
75.93(8)
1
#1
#1
O1–Sr1–O1#
1
O1–Sr1–O7
#
1
1
1
1
1
#1
#1
O2–Sr1–O1#
#1
O2–Sr1–O7#
O5–Sr1–O2
#1
#1
O5–Sr1–O5
O5–Sr1–O7
#
#1
#1
O7–Sr1–O1#
O7–Sr1–O2
O7–Sr1–O5
#1
#1
#1
#1
O7–Sr1–O7
O1 –Sr1–O2
O1 –Sr1–O5
#1
#1
#1
#1
#1
#1
#1
O1 –Sr1–O7
O2 –Sr1–O5
O2 –Sr1–O7
#1
O5 –Sr1–O7
Complex 3
Ni2–O5
Ni2–O22
Ni3–O9
Ni3–O16
2.085(3)
2.14(6)
Ni2–O8
Ni2–N14
Ni3–O12
Ni3–N25
2.006(3)
2.077(3)
2.152(3)
2.052(3)
2.683(3)
2.897(3)
2.761(3)
91.72(12)
91.04(12)
173.33(13)
87.50(13)
91.1(14)
91.41(11)
Ni2–O20
Ni2–N18
Ni3–O13
Ni3–N35
Ba1–O11
Ba1–O19#
2.017(3)
2.033(3)
2.045(3)
2.090(3)
2.788(3)
2.858(3)
3.128(3)
177.6(15)
85.98(11)
86.40(12)
171.80(12)
100.19(14)
89.72(11)
2.005(3)
2.059(3)
2.699(3)
2.695(3)
2.696(3)
88.26(11)
90.56(12)
90.8(10)
86.0(15)
90.1(9)
Ba1–O8
Ba1–O9
Ba1–O13
Ba1–O20
O5–Ni2–O8
O5–Ni2–N14
O8–Ni2–O22
O20–Ni2–O22
N14–Ni2–O22
O9–Ni3–O12
Ba1–O17
Ba1–O23
O5–Ni2–O20
O5–Ni2–N18
O8–Ni2–N14
O20–Ni2–N14
N18–Ni2–O22
O9–Ni3–O13
2
Ba1–O15
O5–Ni2–O22
O8–Ni2–O20
O8–Ni2–N18
O20–Ni2–N18
N14–Ni2–N18
O9–Ni3–O16
84.24(11)
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Table 2 (Contd.)
O9–Ni3–N25
O12–Ni3–O16
O13–Ni3–O16
O16–Ni3–N25
O8–Ba1–O9
O8–Ba1–O17
O8–Ba1–O23
O9–Ba1–O17
O9–Ba1–O23
O11–Ba1–O19
O13–Ba1–O17
O13–Ba1–O23
O17–Ba1–O23
O20–Ba1–O23
174.23(13)
173.76(11)
90.70(12)
95.83(13)
57.67(7)
172.94(8)
90.11(9)
121.39(8)
65.68(9)
77.65(9)
56.15(8)
72.47(9)
95.67(9)
96.91(9)
O9–Ni3–N35
O12–Ni3– N25
O13–Ni3–N25
O16–Ni3–N35
O8–Ba1–O11
O8–Ba1–O19
O9–Ba1–O11
O9–Ba1–O19
O11–Ba1–O13
O11–Ba1–O20
O13–Ba1–O19
O17–Ba1–O19
O19–Ba1–O20
83.75(12)
90.16(13)
86.97(13)
93.92(13)
107.89(8)
111.07(8)
145.91(8)
135.21(8)
115.18(9)
71.30(9)
O12–Ni3–O13
O12–Ni3–N35
O13–Ni3–N35
N25–Ni3–N35
O8–Ba1–O13
O8–Ba1–O20
O9–Ba1–O13
O9–Ba1–O20
O11–Ba1–O17
O11–Ba1–O23
O13–Ba1–O20
O17–Ba1–O20
O19–Ba1–O23
87.89(12)
87.00(12)
173.28(11)
97.39(14)
122.39(8)
61.13(8)
65.25(8)
115.47(8)
68.85(8)
148.41(9)
168.29(8)
121.90(8)
71.61(9)
113.98(9)
74.75(9)
56.57(8)
a
#1
#2
Symmetry transformations used to generate equivalent atoms: ꢀx + 1, ꢀy + 1, ꢀz + 1 (complex 2); ꢀx + 1, y, ꢀz + 3/2 (complex 3).
Fig. 4 (a) View of the molecular structure of complex 1 (hydrogen
atoms and solvent molecules are omitted for clarity, and thermal
ellipsoids are drawn at the 30% probability level). (b) Coordination
Fig. 5 (a) View of the molecular structure of complex 2 (hydrogen
atoms and solvent molecules are omitted for clarity, and thermal
ellipsoids are drawn at the 30% probability level). (b) Coordination
polyhedra for Ni(II) and Sr(II) atoms of complex 2.
polyhedra for Ni(II) and Ca(II) atoms of complex 1.
˚
2
.525(3) A, which are obviously shorter than the distances of
#1
˚
the other two Sr1–O bonds (Sr1–O1 2.667(3) A and Sr1–O1
˚
2
.667(3) A). Obviously, the Sr–O bond lengths in complex 2 are
larger than the corresponding Ca–O bond lengths found in
complex 1.
1
system, space group P2 /n. In complex 3, the terminal Ni(II)
atom (Ni2 or Ni3) is hexa-coordinated with a slightly distorted
octahedral geometry. Where the inner N O cavities of
2
2
Crystal structure of complex 3
4ꢀ
completely deprotonated (L) units as the basal plane, and one
The crystal structure and atom numbering of complex 3 is oxygen atom (O22) from the coordinated methanol molecule,
shown in Fig. 6. Complex 3 crystallizes in the monoclinic crystal the other oxygen atom (O5) from the coordinated H O molecule
2
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for the Ni2 atom. Similarly, one oxygen atom (O12) from the molecules is restricted so that the phenoxo oxygen atoms are
coordinated methanol molecule, the other oxygen atom (O16) directed inward to form an O cavity. Since the O cavity is large,
6
6
from the m-acetate ion for the Ni3 atom. It is unexpected that the the Ca(II), Sr(II) or Ba(II) atoms are suitable for this size, and will
#
2
coordination of two m -acetate ions bridge the Ba1 and Ba1
coordinate to form the C-shaped complexes.
2
atoms in a familiar m
2
-fashion, nally forming a hetero-
The resulting geometries of Ni1 and Ni2 are both distorted
hexanuclear dimer. To our knowledge, this novel 2 : 6 octahedral geometries with hexa-coordinated, Ca1 and Sr1 are
4
ꢀ
2+
(
(L) : M ) heterohexanuclear complex isn't reported in the octa-coordinated with geometries of square antiprisms respec-
1,2e,11c
bis(salamo)-type complexes.
tively. However, Ba1 has bigger size than the cavity, so the
The central Ba1 atom is nona-coordinated with a slightly dis- coordination of metal atoms with the methanol molecules and
torted tricapped trigonal prism geometry, which is different from H O makes the structure more stable. The resulting geometry of
2
the Ca1 and Sr1 atoms. The distances between the Ba1 atom and Ba1 is rarely tricapped trigonal prismatic geometry. As the
the four phenoxy oxygen atoms (O8, O9, O13 and O20) and the m2- cation radius increases, the coordination bond lengths of the
acetate oxygen atom (O23) are ranged from 2.683(3) to 2.761(3) A˚ , central cation are distinctly becoming larger and larger. This
which are evidently shorter than the distances between the Ba1 fact suggests that the radius size of central cation is a signicant
atom and the two methoxy oxygen atoms (O17 and O19) (Ba1–O17 factor which affects binding ability of the central O
6
site. As
site is in
the order of Ca(II) > Sr(II) > Ba(II), which obtained the same
˚
˚
2
2 6
.897(3) A and Ba1–O19 2.858(3) A) and the two m -acetate oxygen a result, the coordinating capability in the central O
#
2
#2
˚
atoms (O11 and O15 ) (Ba1–O11 2.788(3) A and Ba1–O15
3
.128(3) A˚ ).
conclusion with uorescent titration.
As a result, when the two N O salamo moieties are meta-
2
2
lated with d-block transition metals, the conformation of the
Conclusion
Three heterometallic Ni(II)–M(II) (M ¼ Ca, Sr and Ba) complexes
1–3 have been designed and synthesized. X-ray crystal struc-
tures reveal that the different nature of the N
2 2 6
O and O sites of
the ligand H L leads to the site-selective introduction of two
4
different kinds of metal(II) atoms. The coordination number of
Ca(II) Sr(II) and Ba(II) atoms in the O environment are 8, 8 and 9,
6
respectively, and have slightly square antiprism and square
tricapped trigonal prism gemtries. As a result, the coordinating
capability in the central O
Ba(II). Fluorescence titration experiments show that Ni led to
the uorescence quenching of H L. Owing to their electrostatic
interaction and their size-t principle, rare-earth(III) atoms
would easier to occupy the center of the O position success-
6
site is in the order of Ca(II) > Sr(II) >
2
+
4
6
fully, which could be used for the recognition of rare-earth(III)
atoms. The related research is underway.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (21361015 and 21761018) and the Program for
Excellent Team of Scientic Research in Lanzhou Jiaotong
University (201706), which are gratefully acknowledged.
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